BBK 1670 2-1/2" High Flow Performance Full X Pipe With High Flow High Flow Catalytic Converters for Ford Mustang 4.6L BBK is your Number One Aftermarket Performance Exhaust Brand in the USA - American Designed and Built BBK Hi Flow X Pipes are Built with CNC Mandrel Bent Tubing for 35% Increased Flow Over Stock to Increase Horsepower, Torque and Performance 2.5 Inch Full LenGTh X Pipe with Hi Flow 49 State Legal Catalytic Converters Fits all Stock and Aftermarket Shorty Exhaust Headers Bolt on Additional 12-20 Horsepower and More Aggressive Sound, OEM Style Dome Connections for Easy Fitment These BBK Hi Flow Exhaust X Pipes Fit all 1999-2004 Ford Mustang 4.6 GT and Cobra Applications - Aluminized Steel